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The Bureau of Mines is investigating pyrometallurgical and chemical methods for extracting copper from sulfide ores under conditions that provide for control of gaseous and solid emissions. Under this program, a new electrothermic reduction process was developed to produce blister copper after collecting essentially all of the sulfur by a single-unit operation. The process feasibility was indicated by a laboratory-scale investigation that demonstrated chalcopyrite concentrate can be roasted to less than 1 percent sulfur and that the resulting calcine can be reduced with carbon to blister copper by a cyclic process in a single arc-smelting furnace. Pilot-scale tests in an 800-kv-a electric-arc furnace demonstrated that 98.4 pct of the contained copper can be continuously recovered as metal by operating at bath temperatures between 1,350 deg and 1,375 deg c. Smelting rates of approximately 225 lb of blend/ft2 of bath surface/hr resulted in power consumptions of approximately 520 kw-hr/ton of blend. The blister copper that was produced contained less than 0.1 pct iron while the precious metals reporting to the copper product and gangue material elimination were similar to those in a conventional smelting operation.